/* //enter是入场前的刹那（点击按钮），appear指页面第一次加载前的一刹那（自动） */
.fade-enter, .fade-appear {
    opacity: 0;
}
.fade-enter-active, .fade-appear-active { 
    opacity: 1;
    transition: opacity 1s ease-in;
}
.fade-enter-done {
    opacity: 1;
}
.fade-exit {
    opacity: 1;
}

.fade-exit-active {
    opacity: 0;
    transition: opacity 1s ease-in;
}

.fade-exit-done {
    opacity: 0;
}